Which type of hCG test is most useful for diagnosing testicular cancer?

The most useful test for diagnosing testicular cancer is the plasma immunoassay for intact hCG and the β-hCG subunit because this test is specifically designed to identify both the complete molecule of human chorionic gonadotropin (hCG) and its β subunit. Testicular tumors, particularly non-seminomatous germ cell tumors, often produce high levels of β-hCG, which serves as a sensitive tumor marker.

The intact form of hCG consists of both α and β subunits and can provide information about the production of hCG by the tumor. Measuring both forms allows for more accurate assessments regarding the presence of tumors and their activity. In contrast, testing solely for the intact hCG may miss crucial information, while focusing only on the β subunit or using free subunits may not effectively correlate with the tumor's activity. Such distinctions are vital in clinical decision-making and the monitoring of treatment efficacy in testicular cancer patients.